Installer should let to update detected oracle virtualbox

It should also work for OpenJDK installed from .msi file. Detection should read installation information from registry using vbs scripts (see https://msdn.microsoft.com/en-us/library/aa369767(v=vs.85).aspx for details).

Reading install information form registry would work better than detection based on environment variables. It would let rerun detection on installer windows activation and detect changes in configuration without restarting installer.